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7.3
CHAPTER 7
Flash programming
Background information
J-Link comes with a DLL, which allows - amongst other functionalities - reading and
writing RAM, CPU registers, starting and stopping the CPU, and setting breakpoints/
watchpoints. The standard DLL does not have API functions for flash programming.
However, the functionality offered can be used to program the flash. In that case, a
flashloader is required.
7.3.1
How does flash programming via J-Link work ?
Flash programming via J-Link requires extra code. This extra code typically down-
loads a program into the RAM of the target system, which is able to erase and pro-
gram the flash. This program is called RAM code and "knows" how to program the
flash; it contains an implementation of the flash programming algorithm for the par-
ticular flash. Different flash memory devices have different programming algorithms;
the programming algorithm also depends on other things such as endianess of the
target system and organization of the flash memory (for example 1 * 8 bits, 1 * 16
bits, 2 * 16 bits or 32 bits). The RAM code requires data to be programmed into the
flash memory.
7.3.2
Data download to RAM
Data (or part of it) is downloaded to another part of the RAM of the target system.
The program counter (PC) is then set to the start address of the RAM code, the CPU
is started executes the RAM code. The RAM code, which contains the programming
algorithm for the flash memory device, copies data into the flash. The CPU is stopped
after this. This process might have to be repeated until the entire data is pro-
grammed into the flash.
7.3.3
Available options for flash programming
There are different solutions available to program internal or external flashes con-
nected to ColdFire ? cores using J-Link. The different solutions have different fields of
application, but of course also some overlap.
7.3.3.1 Flash loader of compiler / debugger vendor such as IAR
A lot of debuggers (some of them integrated into an IDE) come with their own flash
loaders. The flash loaders can of course be used if they match your flash configura-
tion, which is something that needs to be checked with the vendor of the debugger.
J-Link ColdFire BDM 26 (UM08009)
? 2004-2009 SEGGER Microcontroller GmbH & Co. KG